Ogata K, Kanei-Ishii C, Sasaki M, Hatanaka H, Nagadoi A, Enari M, Nakamura H, Nishimura Y, Ishii S, Sarai A
Tsukuba Life Science Center, Institute of Physical and Chemical Research (RIKEN), Ibaraki, Japan.
Nat Struct Biol. 1996 Feb;3(2):178-87. doi: 10.1038/nsb0296-178.
The DNA-binding domain of Myb consists of three imperfect repeats, R1, R2 and R3, each containing a helix-turn-helix motif variation. Among these repeats, R2 has distinct characteristics with high thermal instability. The NMR structure analysis found a cavity inside the hydrophobic core of R2 but not in R1 or R3. Here, we show that R2 has slow conformational fluctuations, and that a cavity-filling mutation which stabilizes the R2 structure significantly reduces specific Myb DNA-binding activity and trans-activation. Structural observations of the free and DNA-complexed stages suggest that the implied inherent conformational flexibility of R2, associated with the presence of the cavity, could be important for DNA recognition by Myb.
Myb的DNA结合结构域由三个不完全重复序列R1、R2和R3组成，每个重复序列都包含一种螺旋-转角-螺旋基序变体。在这些重复序列中，R2具有独特的特征，热稳定性较差。核磁共振结构分析发现R2的疏水核心内部有一个空腔，而R1或R3中没有。在此，我们表明R2具有缓慢的构象波动，并且一个稳定R2结构的空腔填充突变显著降低了Myb特异性DNA结合活性和反式激活。对游离和DNA复合阶段的结构观察表明，与空腔的存在相关的R2隐含的固有构象灵活性可能对Myb识别DNA很重要。
